Heart disease converts to the clinical syndrome of heart failure when the cardiac output is inadequate to meet metabolic requirements. Evidence now supports that pharmacological targeting of Ca2???? dependent protein kinase II (CaMKII), a sensor of dysregulated calcium homeostasis, will inhibit conversion of early stages of cellular pathophysiology to symptomatic heart failure and sudden death. Inhibition of the kinase with research inhibitors, or by genetic knock-out of the major cardiac isoform, blocks this chain of events in animal models. We propose a strategy to modify a small molecule inhibitor of CaMKII to increase its potency and selectivity, test it biochemically to ensure it has the desired mechanism of action, then test for inhibition of characterized markers of hypertrophy and for apoptosis in neonatal mouse cardiomyocytes. We start with an allosteric CaMKII inhibitor used to demonstrate its cardiovascular functions but has never been pharmacologically optimized and thus have low potency. Guided by our analysis of new crystal structures and structural insights we have developed from docking inhibitors to its active site we have designed a set of compounds that target a unique feature of the allosteric pocket in the active site of CaMKII. Our overall goals for Phase I are to retain and improve the selectivity of the inhibitor while markedly increasing its potency, and to test the lead inhibitor compounds for efficacy then test for inhibition of characterized markers of hypertrophy and for apoptosis it in neonatal mouse cardiomyocytes PUBLIC HEALTH RELEVANCE: Heart failure is a global burden, with the lifetime risk in the developed world above 20% and a consuming focus for patients, clinicians, scientists, and policymakers. Heart disease converts to the clinical syndrome of heart failure when the cardiac output is inadequate to meet metabolic requirements. Evidence now supports that pharmacological targeting of intracellular signaling, in particular of Ca2???? dependent protein kinase II, a sensor of dysregulated calcium homeostasis will inhibit conversion to symptomatic heart failure and sudden death. We propose a strategy to modify a small molecule inhibitor of this protein kinase in ways that increase its potency, analyze it biochemically to ensure it has the desired mechanism of action, then test for inhibition of characterized markers of hypertrophy and for apoptosis it in neonatal mouse cardiomyocytes.